1. Field of the Invention
The present invention relates to a synchronizing device in a motor vehicle gearbox.
2. Background Art
When shifting gears in a gearbox of this kind the time it takes to complete the engagement process and the force that the driver has to apply on the gear shift lever largely depend on the size of the blocking angle of the teeth on the engaging sleeves and on the synchronizing rings. A large blocking angle requires a larger force on the gear shift lever and a longer synchronizing and engagement time. On the other hand one assures that the synchronizing process is completed when the teeth of the engaging sleeve engage with the teeth of the clutch discs. A smaller blocking angle requires less force on the gear shift lever and a shorter time before the engaging sleeve engages the clutch discs, but instead there is a risk that the synchronizing process has not been completed when the teeth of the engaging sleeve hit the teeth of the clutch disc.
Since the friction torque is larger in multi synchronizing ring synchronizer systems than in single ring synchronizer systems; one can use synchronizing rings with a smaller blocking angle in multi (double or triple) ring systems than in single ring systems without risking that the synchronizing process has not been completed before the teeth of the engaging sleeve hit the teeth of the clutch discs. It is known in the art to use both single and multi ring synchronizer systems in a single gearbox. Usually multi ring synchronizer systems are used for the lower gears, e.g. first, second and third gears, which require larger synchronizing torque than the higher gears. Usually single ring systems are used for the higher gears.
In order to optimize shift quality in such gearboxes the components of the multi ring synchronizer systems should have teeth with a smaller blocking angle than the single ring synchronizer systems. However, this requires the manufacture and the assembly of, among other things, at least two and in some cases even three, different engaging sleeves, one having teeth with a smaller blocking angle at both ends, one having teeth with a larger blocking angle at both ends and one having teeth with a smaller angle at one end and a larger angle at the opposite end. Of course this increases the cost compared with a gearbox having only one kind of engaging sleeve. There is also a risk for mixing the various engaging sleeves when assembling the gearboxes. In order to reduce costs and eliminate the risk for errors in the assembling process it is previously known to use engaging sleeves having the same blocking angle for single and multi ring synchronizer systems. In such cases a larger than necessary blocking angle has to be used for the multi ring synchronizer systems which means that shift quality will not be optimized for all gears.
A purpose of the present invention is to achieve a synchronizing device of the type described by way of introduction, by means of which it possible to use one and the same engaging sleeve for synchronizing rings and clutch discs having teeth with different blocking angles.
This is achieved according to the invention by virtue of the fact that the teeth on the engaging sleeve are divided into at least a first and a second group, the teeth of the first group having V-shaped end surfaces with a first blocking angle while the teeth of the second group have V-shaped end surfaces with a second blocking angle different from the first blocking angle, and that the first synchronizing ring has blocker teeth with a V-shaped end surface having said first blocking angle in areas facing said first teeth group on the engaging sleeve and lacks teeth in intermediate areas facing the second teeth group, while the second synchronizing ring has blocker teeth with a V-shaped end surface having said second blocking angle in areas facing said second teeth group and lacks blocker teeth in intermediate areas facing the first teeth group.
A synchronizer according to this invention includes a synchronizer hub, intended to be non-rotatably joined to a shaft in a gearbox, an engaging sleeve, which is non-rotatably but axially displaceably mounted on the synchronizer hub by means of interengaging external teeth on the synchronizer hub and internal teeth on the engaging sleeve, first and second clutch discs provided with external teeth and mounted on each side of the synchronizer hub, said discs being designed to be non-rotatably joined to a first and second gear wheel rotatably mounted on said shaft on each side of the synchronizer hub and being lockable relative to the synchronizer hub by axial displacement of the engaging sleeve from a neutral to an engaging position, in which the internal teeth on the engaging sleeve engage with the external teeth on the clutch discs, and first and second synchronizing rings mounted on each side of the synchronizer hub between the hub and the clutch discs, each synchronizing ring having external blocker teeth engaging with the internal teeth on the engaging sleeve and an internal conical friction surface engaging with an external friction surface on an element non-rotatably joined to each clutch disc when the engaging sleeve is displaced from the neutral position to an engaging position, the internal teeth on the engaging sleeve having opposite V-shaped end surfaces facing corresponding V-shaped surfaces on the synchronizing ring blocker teeth and the clutch disc teeth.
The invention is based on the fact that it is not necessary that teeth along the whole circumference of the engaging sleeve and the synchronizing rings are effective to transmit torque during the synchronizing process. When teeth along the whole circumference of the engaging sleeve and the synchronizing ring are divided into two groups only half of the total amount of teeth are effective on each side.